Physical Therapy Assistant Practice Exam 2025 - Free PTA Practice Questions and Study Guide

The crossed extension reflex is a protective reflex that occurs when one limb is withdrawn from a painful stimulus, resulting in an opposite compensatory response in the contralateral limb. Specifically, when a leg that has been stimulated (often due to pain) flexes to withdraw from the stimulus, the opposite leg undergoes an extension response to support the body and maintain balance.

Thus, the correct response indicates that the opposite leg extends while also flexing at the hip and knee to stabilize the individual, allowing weight to be shifted toward the extended leg. This extension in the opposite leg serves to counterbalance the weight of the body when the affected leg is retracted, thus preventing falls or instability.

The other options contain variations of flexion and extension that do not accurately reflect the typical response. The crossed extension reflex primarily involves the extension of the opposite leg to maintain posture and react to the stimulus effectively.